GRB 050421: Swift-UVOT observation. Blustin, A. ; Barbier, L. ; McGowan, K. ; Roming, P. ; de Pasquale, M. ; Holland, S. T. ; Gehrels, N. ; Mason, K. ; Nousek, J. Abstract Publication: GRB Coordinates Network Pub Date: 2005 Bibcode: 2005GCN..3307....1B